Senior Developer (Freelance Onsite London Contract)

Underwaterpistol (Shopify Plus Agency); Birmingham; Hybrid; GBP 80,000 - 100,000; Part time

Job summary

A creative ecommerce agency is seeking a Senior Developer for a short-term freelance position based in London. The ideal candidate will work directly with clients to create impactful ecommerce experiences using Shopify. Responsibilities include building front-end features and ensuring code quality. Required skills include proficiency in HTML5, CSS3, and JavaScript, as well as experience with Shopify and Liquid. The position offers flexibility with remote work and a competitive rate.

Qualifications

• Experience with Shopify essential.
• Strong proficiency with HTML5, CSS3, and Vanilla JavaScript.
• Experience working with Liquid, understanding LESS and SASS.

Responsibilities

• Build design comps accurately and efficiently.
• Write structured, organized, reusable code.
• Inspect, debug, and troubleshoot bugs.

Skills

Experience with Shopify

Strong proficiency with HTML5

Strong proficiency with CSS3

Strong proficiency with Vanilla JavaScript

Experience working with Liquid (Shopify)

Understanding of LESS and SASS pre‑processing

Strong grasp of cross‑browser compatibility

Proficiency with Git

Understanding of SEO and UX best practices

Excellent attention to detail

Strong communication and documentation skills

Portfolio of live projects

Job description

Location: 1 day remote + 1 day on‑site in London

Contract: Freelance, approx. 3‑month rolling project

Reports to: Technical Lead

Rate: £250 - £350 per day

Start: ASAP

Intro

We’re looking for an experienced Senior Developer to join us on a short‑term freelance basis, working directly on‑site with our London‑based clients two days a week. We’re looking for a self‑motivated Senior Developer who’s confident in client‑facing environments, able to advocate for the best use of their time, and skilled in shaping tasks as well as delivering work autonomously.

You’ll help bring high‑impact ecommerce projects to life, turning design concepts into fast, accessible and beautiful experiences that perform flawlessly.

About UWP

We’re Underwaterpistol, a creative and technical ecommerce agency built for brands that want to stand out. We design, build and grow Shopify Plus stores that deliver measurable results, blending creative thinking with technical precision.

Our developers care deeply about quality, detail, and craft and we’re looking for someone who shares that mindset.

This role involves working closely with our clients on‑site, acting as a trusted technical partner. You’ll be responsible for shaping your workload, managing priorities directly with client teams as their primary solo developer and representing UWP with confidence and clarity.

Role Overview

As a Senior Developer, you’ll lead the build and implementation of front‑end features, ensuring clean, reusable code and seamless collaboration with designers and strategists. You’ll be hands‑on in translating UI/UX concepts into working digital experiences, maintaining our high standards for accessibility, performance, and maintainability.

You’ll need to be comfortable working independently, shaping tasks proactively, and advocating for the most effective use of development time in a client‑facing setting.

Key Responsibilities

• Build out design comps accurately and efficiently.
• Write structured, well‑organised, reusable code.
• Inspect, debug, and troubleshoot bugs and QA issues.
• Ensure the technical feasibility of UI/UX designs.
• Collaborate closely with other team members and stakeholders.
• Lead on assigned development projects, making technical recommendations, flagging risks, and supporting other developers when needed.
• Help uphold and refine UWP’s development standards and best practices.
• Contribute to internal policies, documentation, and component frameworks.
• Communicate progress clearly with project and delivery teams, ensuring visibility on timelines and blockers.

Skills and Experience

Essential

• Experience with Shopify
• Strong proficiency with HTML5, CSS3, and Vanilla JavaScript
• Experience working with Liquid (Shopify)
• Understanding of LESS and SASS pre‑processing
• Strong grasp of cross‑browser compatibility and responsive development
• Proficiency with Git (or similar version control)
• Understanding of SEO and UX best practices
• Excellent attention to detail and a good eye for design
• Strong communication and documentation skills
• Portfolio of live projects demonstrating your work

Nice to Have

• Experience with Gadget
• Familiarity with JavaScript frameworks (React, Vue, Angular)
• Experience with Node.js, Python, Ruby, or PHP